According to a continuous demand for improvement of fuel efficiency for a vehicle and stricter regulations of discharge gas of countries, a demand for an environmentally-friendly vehicle has increased, and a hybrid vehicle has been provided as a realistic alternative for the demand.
As a power source, an engine and a motor are applied to the hybrid vehicle, and depending on driving conditions, features of the engine and the motor are embodied to provide fuel efficiency and a reduction of exhaust gas. The hybrid vehicle may provide output torque depending on how the two power sources consisting of the engine and the motor are harmoniously operated.
For the hybrid vehicles, a TMED (Transmission Mounted Electric Device) type of power train is generally used, an engine clutch is disposed between the two power sources (engine and motor), and they travel in an EV (electric vehicle) mode or an HEV (hybrid electric vehicle) mode in accordance with engagement of the engine clutch. When the engine clutch is disposed between the two power sources (engine and motor), it is difficult to control to engage the engine clutch.
Meanwhile, when the engine clutch is engaged in order to transit from an EV (electric vehicle) mode to an HEV (hybrid electric vehicle) mode is performed, the hybrid vehicle determines slip of the engine clutch in order to reduce impact and improve driving performance.
Generally, slip of the engine clutch is determined as follow. A command pressure (hydraulic pressure) for engaging the engine clutch is stored through learning while stopping, and it is determined that the engine clutch is engaged when a real time command pressure is greater than the stored command pressure. However, according to conventional art, since the engagement of the engine clutch is influenced by the external environment (for example, temperature, viscosity of oil, aging of parts, etc.), determination of the slip is inaccurate.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.